1. In my vision of D&D, all characters exist in their own little bubble that has its own laws of physics. So if the party contains Lao the Badass Kung Fu Monk, Gritty McGritster the Merc, and Sir Toby the Bold, each can have their own style. Lao can balance on people's swords and kick them in the face, McGritster can be covered in mud and other people's blood, and Sir Toby can spend half the fight talking in terrible pseudo medieval pidgin ("Have at thee, foul rogue! Huzzah!"). Everybody gets to do their own thing. And if McGritster's player can't stand the fact that other people are doing a thing that he doesn't like, he can go game somewhere else.
I think the same is true for a game's art.
2. Artwork depicting female characters should be (mostly) designed to appeal to female players. Each individual female player should be able to find at least some character art that appeals to her. That doesn't mean that none of it should be sexy. Some female players like the idea of highly sexualized characters. But not all of them do! The few who do should not be an excuse for male gamers to fill the books with female "character art" that is really just pinup art for their own enjoyment.
3. If artwork is included for purely pinup purposes, it should cover both genders. Male gamers uninterested in pinup art of male models can look past it just like women do. Being a grownup is all about sharing. If you get yours, other people get theirs.
4. If the RPG community can't accept these reasonable standards, then... I don't know. That fact will say something about us. I'm not sure what.